This invention relates to optoelectronic devices, and particularly to components and techniques for automatically, and "purely mechanically," interconnecting arrays of optical fibers with waveguide arrays.
The problem addressed by the present invention, as well as various solutions therefor, are known, see, for example, E. J. Murphy, "Fiber Attachment for Guided Wave Devices", J. Lightwave Tech., Vol. 6, No. 6, 6/88, pp. 862-871, and W. Hunziker et al, "Self-Aligned Optical Flip-Chip OEIC Packaging Technologies", Proc. ECOC, 1993, pp. 84-91 and U.S. Pat. Nos. 4,639,074 and 4,725,114, both to E. J. Murphy, the subject matter of which is incorporated herein by reference. Briefly, in various optical-electronic systems, e.g., telecommunication systems, it is the practice to mount various optical components, e.g., lasers, optical waveguide switch matrices, etc., on a mounting board and to interconnect the various components by means of optical waveguides formed on a surface of the mounting board. The waveguides are connected to optical fibers for signal transmission. Efficient assembly of the systems requires that the ends of the optical fibers be precisely aligned with and abutted against the ends of the waveguides. The present invention is directed to the problem of automatically interconnecting arrays of optical fibers with arrays of waveguides mounted on waveguide mounting boards. Also, as discussed in the cited references, the interconnecting is preferably done "purely mechanically," i.e., without the need for actually operating the devices being assembled together for monitoring and maximizing coupling efficiencies as part of the assembly process.
In one known technology, an array of fibers is disposed in a corresponding array of parallel V-grooves on a substrate which includes two empty V-grooves in precise relationship with the fibers. An array of waveguides, corresponding to the fiber array, is disposed on a second substrate which includes alignment ridges in precise relationship with the waveguides. In the assembly process, the two substrates are disposed in overlapping relationship with the ridges being disposed within the empty V-grooves for aligning the two substrates in contacting relationship. The ridges comprise elongated blocks having rectangular top surfaces, and precise alignment is obtained by engagement of elongated edges of the ridge top surfaces with the side walls of the V-grooves. End-to-end abutting relationship between the waveguides and the fibers is obtained by sliding the fiber substrate along the ridges until the ends of the fibers abut against ends of the waveguides.
While the prior known technology is functional, two problems are present. One problem arises from the fact that, in order to obtain precise alignment of the ridges with the waveguides on the waveguide substrate, the ridges are made using photolithographic and etching techniques involving etching into the surface of the substrate. While precision is obtained, the problem is that only relatively small ridges are obtained which are relatively fragile. During assembly, alignment of the two substrates is provided by sliding contact of the ridge upper surface edges with the sides of the V-grooves, and rupture of the edges frequently occurs.
Another problem of the process is that the ridges are formed separately from the waveguides, and the final accuracy is a function of how accurately the ridges are registered with the waveguides. Some inaccuracy inevitably results and, in any event, the separate processing procedures add expense.